1. Field of the Invention
The present invention relates to tube bending apparatuses, and more particularly to an improved die and tube bending apparatus configured to produce noncircular bends in tubes.
2. Discussion of Prior Art
Conventional tube-bending apparatuses primarily employ compression, press and rotary draw methods to bend tubes along circular arcs. These apparatuses and methods are commonly utilized in various industries, including automobile and aircraft assembly, plumbing and fire protection, and equipment/conduit manufacture. These apparatuses typically include a set of dies and a drive mechanism that cooperate to impart pressure upon the tube, so that the tube bends to a predetermined form. More particularly, a bend die is positioned adjacent to a section of the tube and the apparatus is configured to conform the section to the circular profile defined by the bend die. The engaging surface of the bend die is-formed by a constant radius, and therefore produces a change in radius at the beginning of the bend equal to the difference between the constant radius and the radius of the virtually straight tube prior to the bend. Once released, a minor degree of spring-back occurs to result in the final orientation of the bent tube.
These conventional apparatuses and methods, however, present a plurality of concerns to those ordinarily skilled in the art, as well as the targeted consumer. Of primary concern, is deformation that frequently occurs during the bending process. During these deformed bends, the tube collapses on the outer side, and compresses on the inner side of the tube to produce flat or concave spots and wrinkles respectively; and the likelihood of deformation is based in part on the outer tube diameter, wall thickness, and radius of curvature of the bend. These deformed bends may result in increased costs and inconvenience, both during the fabrication and utilization of the tube. For example, where a mandrel is initially inserted into the tube to facilitate bending, a small degree of deformation may inhibit the removal of the mandrel, and thereby result in inefficiencies to the overall fabrication process, where the tube is utilized as a conduit, the reduced cross sectional area of the deformed bend results in a decreased capacity of flow, and finally, where the bent tube is utilized proximate an operator/end user, as in a bicycle frame, the wrinkles may result in abrasions to the operator or damage to fabric coming in contact therewith.
Even where properly formed, conventionally bent tubes present concerns. During the network installation of a bent tube, for example, the lack of geometric flexibility in the configuration of the produced bends limits the efficient use of space. This can be seen in the congested space of the undercarriage of an automobile, where the limitations to circular and combinations of circular bends of exhaust tubing often limit design configurations. Where utilized as a conduit, the abrupt change in radius caused by conventional apparatuses and methods also results in a greater dissipation of fluid energy.
Accordingly, there is a need in the art for an improved apparatus for and method of bending tubes that reduces the likelihood of deformation and provides greater geometric flexibility during installation.